Precise dynamic race detectors provide strong correctness guarantees but have high overheads because they generally keep analysis state in a separate shadow location for each heap memory location, and they check (and potentially update) the corresponding shadow location on each heap access. The BigFoot dynamic race detector uses a combination of static and dynamic analysis techniques to coalesce checks and compress shadow locations. With BigFoot, multiple accesses to an object or array often induce a single coalesced check that manipulates a single compressed shadow location, resulting in a performance improvement over FastTrack of 60% with no loss of precision.